The wisdom teeth, or third molars, are the final set of teeth to develop, typically emerging between the ages of 17 and 25. They earned their common name because this period is traditionally associated with reaching maturity. While these molars were once necessary for ancestors who processed coarse, raw foods, the evolution of softer diets and smaller human jaws has led to a mismatch between tooth size and jaw space, often necessitating their removal.
Impaction and Abnormal Growth
The primary reason third molars cause problems is a lack of sufficient space at the back of the jaw for them to erupt fully. When the tooth is unable to emerge completely through the gum line, it is considered impacted, meaning it is partially or fully trapped beneath the soft tissue or bone. This abnormal positioning prevents the tooth from aligning properly, which can hinder normal chewing function.
Dental professionals classify impaction based on the angle at which the tooth is growing. A common type is the mesial impaction, where the tooth is angled forward, pressing into the second molar directly in front of it. Conversely, a distal impaction angles toward the back of the mouth, though this is a less frequent occurrence.
A more problematic orientation is the horizontal impaction, where the tooth lies completely on its side, parallel to the jawbone. This sideways growth means the crown pushes directly against the root of the adjacent molar. Even a vertical impaction, where the tooth grows straight up, can remain trapped beneath the gum line, leading to issues later on.
Damage to Surrounding Teeth and Structures
The chronic pressure exerted by a misaligned wisdom tooth can have serious consequences for its neighbors and the surrounding bone. When the third molar is angled forward, such as in a mesial or horizontal impaction, it pushes against the second molar. This constant force can lead to crowding or shifting of existing teeth, which is concerning for individuals who have had previous orthodontic treatment.
The pressure from an impacted wisdom tooth can trigger external root resorption, a process where the root structure of the healthy second molar begins to dissolve due to chronic force and inflammation. This damage is often irreversible, compromising the second molar’s structural integrity and potentially leading to its eventual loss.
Impacted teeth develop within a sac in the jawbone that can fill with fluid to form a dentigerous cyst. As the cyst expands, it erodes the surrounding bone tissue, weakening the jaw structure. While these cysts are typically benign, their unchecked growth can displace adjacent teeth and damage nerves, requiring complex surgical intervention.
Infection, Decay, and Disease
A partially erupted wisdom tooth creates an environment where harmful bacteria thrive, leading to painful infections. The partially emerged tooth leaves a flap of gum tissue, known as an operculum, draped over the crown. Food debris, plaque, and bacteria easily become trapped beneath this flap, a location nearly impossible to clean with regular brushing and flossing.
This accumulation of bacteria frequently results in pericoronitis, an inflammatory infection of the soft tissues surrounding the tooth. Symptoms include severe localized pain, swelling, and sometimes the discharge of pus, indicating an active infection. If this infection spreads, it can lead to more serious conditions like cellulitis, affecting the throat and neck.
The difficulty in maintaining hygiene around these back molars significantly increases the risk of dental decay, or caries. Trapped food and bacteria attack the enamel of both the wisdom tooth and the neighboring second molar. Cavities on the wisdom tooth are often difficult to treat due to its position, making extraction a more practical solution than restoration.
The same conditions that cause infection can also lead to periodontal disease, or gum disease, in the immediate area. The chronic presence of plaque and inflammation can destroy the bone and ligaments supporting the second molar. Removing the wisdom tooth often eliminates the source of infection and prevents the progressive destruction of the supporting structures for the rest of the teeth.